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The County of San Mateo has added a translation feature developed by Google Translate to assist web visitors in understanding information on this website in a variety of foreign languages. Please be aware that Google Translate, a free third party service which the County does not control, provides automated computer translations that may not give you an exact translation. The County cannot guarantee the accuracy of translations through Google Translate so translations should not be considered exact and only used as a rough guide. Anyone relying on information obtained from Google Translate does so at his or her own risk. The County disclaims and will not accept any liability for damages or losses of any kind caused by the use of the Google Translate feature.


Transportation Demand Management

Case Study – King County: Strategies for Right Sizing Parking


The King County Right Size Parking (RSP) project, funded by a three-year grant from the Federal Highway Administration’s Value Pricing Pilot Program, assembled local information on multi-family residential parking demand to guide parking supply and management decisions. The objectives of the project were to:

  • Support economic development by reducing barriers to building mixed-use, multi-family residential developments in urban centers near transit;
  • Reduce housing costs as well as household monthly expenditures, allowing a wider market demographic to participate in the urban infill housing market;
  • Encourage transit use, rideshare, bicycling and walking; and
  • Reduce vehicle miles traveled (VMT) and greenhouse gases (GHG) emissions.

RSP research found on average that more than 40% of parking spaces went unused, often in walkable locations with nearby shops, stores, and restaurants and access to public transit.  The report of research findings noted that construction of parking in multi-family projects costs $20,000 to $40,000 per stall, which impacts rental prices. Based on this research, the RSP Project produced a Technical Policy Memorandum summarizing known barriers and potential solutions for RSP. This included a Right Size Parking Model Code that supports housing affordability and neighborhood walkability based on the RSP Project data and a RSP web-based Calculator which provides context-sensitive information on parking demand. The project also provides resources for developers – a Multi-family Parking Strategies Toolkit to help developers and property managers to better manage parking supply in multifamily buildings, and a Parking Requirements and Utilization Gap Analysis that identified misaligned parking requirements.

King City Model Transformations

RSP Calculator:

The RSP Calculator was developed by King County Metro, the transportation authority for the County, with support from the Center for Neighborhood Technology and the Urban Land Institute Northwest. It can estimate parking usage for different types of multifamily developments based on building type, location, unit and parking pricing, and proximity to transit and job locations. Additionally, the tool automatically calculates and displays parking utilization estimates for parking pricing bundled with or unbundled from rent, and 100% affordable units or no affordable units.

Parking Model Code:

The RSP Model Code project encourages local jurisdictions to match their parking supply to the actual demand. The model parking code is comprised of two approaches: market-based and context-based. In the market-based approach, there are no minimum parking requirements; rather, the market determines the amount of parking. This approach most effectively matches parking supply with parking demand so that developers are not forced to build more parking than is needed.

With the context-based approach, minimums are set based on the unique context and characteristics of a given project. The process has two steps. First, a generalized place type and associated base parking minimum is assigned. The proposed types are urban core, mixed-use center, and suburban commercial/residential neighborhood. Second, a series of adjustments are applied to that base minimum to account for specific building and contextual features, such as housing unit type, resident characteristics, transportation alternatives, off-street parking management, and parking stall substitutions.

Challenges and Lessons Learned

Having robust, accurate data from the local jurisdiction is crucial to developing the RSP calculator. King County focused on multi-family housing and collected data in the middle of the night from multi-family projects to ensure accuracy. King County has now updated the calculator due to the substantial growth in the county that is seen as continuing and changing land use. The key policy implication from the RSP project is that there is generally an oversupply of parking. Reducing parking requirements encourages greater transit use and enables more frequent transit service.

Despite the data demonstrating that parking is typically overbuilt, localities may still face resistance to reform. For example, the City of Kirkwood faced local opposition when they considered amending their parking requirements. Another challenge is educating developers and lenders about actual parking needs, since many still believe that they must supply additional parking on site in order to market their projects to prospective residents.

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